Various techniques are used on spinning machines to resume spinning (yarn production), after an interruption of the spinning process has occurred, whether it is after an accidental yarn break, or after a controlled interruption of spinning upon receipt of a signal from a yarn quality sensor or also after the replacement of a fully wound bobbin with an empty tube.
The purpose of the preparation of a workstation for the resumption of the spinning process is to ensure that the individual machine parts of the workstation and, if necessary, also the parts of an attending device, adopt the required position or setting, so that the spinning-in yarn end onto which the spinning-in will take place is prepared, and to ensure that the spinning-in yarn end is situated in a defined initial position for starting the spinning-in process.
In the case of a sudden interruption of spinning, e.g., due to a yarn break, it is generally such a fast process that controlled stopping of the machine workstation cannot be applied and the torn yarn end is wound onto the bobbin. To resume the spinning process, it is necessary to detect the yarn end on the bobbin, by means of an attending device or manually, to remove the defective yarn portion by unwinding it from the bobbin, and to guide the yarn into the working path or to a position in which it can be easily passed on to the workstation means. At the same time, for the resumption of the spinning process, it is necessary for the yarn end to be situated in the so-called transfer position with respect to the spinning nozzle for further operations at the working station and so that it can be delivered to the spinning nozzle for performing the final steps of the preparation of the workstation for the resumption of the spinning process.
Analogous to this situation is also the preparation of the workstation to resume the spinning process after the replacement of a fully wound bobbin with an empty bobbin, when the yarn end is not detected on the wound bobbin, but it is spun onto auxiliary yarn, which is usually carried by the attending device on a bobbin of auxiliary yarn. The attending device prepares the auxiliary yarn so that it could be promptly delivered to the means of the workstation. The end is placed by the attending device into the so-called transfer position for further operations at the working station and for being inserted into the spinning nozzle so that the final steps of the preparation of the workstation of the air-jet spinning machine for the resumption of the spinning process can be performed.
When the interruption of spinning is carried out in a controlled manner, e.g. after a signal from the yarn quality sensor has been produced, the machine parts of the workstation gradually decelerate in a coordinated manner until they come to a complete stop, i.e. to the interruption of spinning, whereby the yarn remains in the working path at the working station, its end being situated in the spinning nozzle, and so it is not necessary to detect it on the bobbin or set it to the so-called transfer position for further operations at the working station and for insertion into the spinning nozzle so as to perform the final workstation preparation steps for the resumption of the spinning process.
The aforementioned final workstation preparation steps consist in delivering the yarn end from the transfer position to the spinning nozzle and then in unwinding the required length of the yarn against the direction of the fiber feed to the spinning nozzle during normal spinning in front of the spinning nozzle, where is arranged a device for the preparation of the spinning-in yarn end, which forms the spinning-in yarn end on the unwound yarn. In the meantime, the other machine parts of the workstation get ready for starting the spinning-in process, including the formation of yarn reserve in an underpressure yarn storage device by the unwinding of the yarn from the bobbin, thus preparing the workstation for the resumption of the spinning process.
The above-mentioned techniques are disclosed, for example, in DE 10 2012 108 380 A1.
The problem of the background art is the variability of the position of the spinning-in yarn end formed by the device for the preparation of the spinning-in yarn end, which consequently leads to a deterioration in the uniformity of the piecing parameters. Due to the requirements for the spinning-in, it is also necessary to create a sufficiently long spinning-in yarn end for starting the spinning-in process. Moreover, it is advisable for the device for forming the spinning-in yarn end to be accessible to the machine operators.